package DoExercise.HSP_ZCY.A008_树.A001_普通二叉树.二叉树递归套路_找可能性;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;


/**
 * 一颗二叉树，任何两个节点之间都存在距离
 * 求这颗二叉树节点间的最大距离
 */
public class Code08_二叉树的最远距离
{

    public static class Node
    {
        public int value;
        public Node left;
        public Node right;

        public Node(int data)
        {
            this.value = data;
        }
    }

    public static int maxDistance1(Node head)
    {
        if (head == null)
        {
            return 0;
        }
        ArrayList<Node> arr = getPrelist(head);
        HashMap<Node, Node> parentMap = getParentMap(head);
        int max = 0;
        for (int i = 0; i < arr.size(); i++)
        {
            for (int j = i; j < arr.size(); j++)
            {
                max = Math.max(max, distance(parentMap, arr.get(i), arr.get(j)));
            }
        }
        return max;
    }

    public static ArrayList<Node> getPrelist(Node head)
    {
        ArrayList<Node> arr = new ArrayList<>();
        fillPrelist(head, arr);
        return arr;
    }

    public static void fillPrelist(Node head, ArrayList<Node> arr)
    {
        if (head == null)
        {
            return;
        }
        arr.add(head);
        fillPrelist(head.left, arr);
        fillPrelist(head.right, arr);
    }

    public static HashMap<Node, Node> getParentMap(Node head)
    {
        HashMap<Node, Node> map = new HashMap<>();
        map.put(head, null);
        fillParentMap(head, map);
        return map;
    }

    public static void fillParentMap(Node head, HashMap<Node, Node> parentMap)
    {
        if (head.left != null)
        {
            parentMap.put(head.left, head);
            fillParentMap(head.left, parentMap);
        }
        if (head.right != null)
        {
            parentMap.put(head.right, head);
            fillParentMap(head.right, parentMap);
        }
    }

    public static int distance(HashMap<Node, Node> parentMap, Node o1, Node o2)
    {
        HashSet<Node> o1Set = new HashSet<>();
        Node cur = o1;
        o1Set.add(cur);
        while (parentMap.get(cur) != null)
        {
            cur = parentMap.get(cur);
            o1Set.add(cur);
        }
        cur = o2;
        while (!o1Set.contains(cur))
        {
            cur = parentMap.get(cur);
        }
        Node lowestAncestor = cur;
        cur = o1;
        int distance1 = 1;
        while (cur != lowestAncestor)
        {
            cur = parentMap.get(cur);
            distance1++;
        }
        cur = o2;
        int distance2 = 1;
        while (cur != lowestAncestor)
        {
            cur = parentMap.get(cur);
            distance2++;
        }
        return distance1 + distance2 - 1;
    }

    public static int maxDistance2(Node head)
    {
        return process(head).maxDistance;
    }

    public static class Info
    {
        public int maxDistance;
        public int height;

        public Info(int dis, int h)
        {
            maxDistance = dis;//最大距离
            height = h;//高度
        }
    }

    public static Info process(Node head)
    {
        if (head == null)
        {
            return new Info(0, 0);
        }
        Info leftInfo = process(head.left);
        Info rightInfo = process(head.right);
        int height = Math.max(leftInfo.height, rightInfo.height) + 1;
        // 与head有关系和与head没关系两种结合，但是重点是考虑对某个X节点来说，X的最大节点距离是多少？
        //有关系 leftInfo.height + rightInfo.height + 1
        //没关系 Math.max(leftInfo.maxDistance, rightInfo.maxDistance)
        int maxDistance = Math.max(Math.max(leftInfo.maxDistance, rightInfo.maxDistance), leftInfo.height + rightInfo.height + 1);
        return new Info(maxDistance, height);
    }

    // for test
    public static Node generateRandomBST(int maxLevel, int maxValue)
    {
        return generate(1, maxLevel, maxValue);
    }

    // for test
    public static Node generate(int level, int maxLevel, int maxValue)
    {
        if (level > maxLevel || Math.random() < 0.5)
        {
            return null;
        }
        Node head = new Node((int) (Math.random() * maxValue));
        head.left = generate(level + 1, maxLevel, maxValue);
        head.right = generate(level + 1, maxLevel, maxValue);
        return head;
    }

    public static void main(String[] args)
    {
        int maxLevel = 4;
        int maxValue = 100;
        int testTimes = 1000000;
        for (int i = 0; i < testTimes; i++)
        {
            Node head = generateRandomBST(maxLevel, maxValue);
            if (maxDistance1(head) != maxDistance2(head))
            {
                System.out.println("Oops!");
            }
        }
        System.out.println("finish!");
    }

}
